“both…and…”起连接词作用，作“两者都”、“又……又”、“不但……而且”解：
注意：“both…and…”能连接各种并列成分，甚至两个句子。
1.Both copper and silver are good conductors of
electricity.(连接两个主语)铜和银都是良好的电导体。
2.The molecules of common salt all contain atoms of both the gas and the
metal which compose the salt.(连接of的两个宾语)食盐分子都具有构成食盐的气体和金属这两种物质的原子。
3.Alloys are both useful and important.(连接两个表语)合金既有用又重要。
4.To do work, you must both exert force and move
something.(连接两个动词短语)为了作功，你必须既施加力又推动某个东西。
5.Copper is an important conductor, both because of its high conductivity
and because of its abundance and low
cost.(连接两个状语)铜是一种重要的导体，因为它的导电率高，而且资源丰富，价格又低。
6.It is necessary to build a lot of petrochemical works, both because China
is rich in petroleum and because there is a great demand for
petrochemicals.(连接两个状语从句)由于中国石油丰富，而对石油化学产品需要量又大，所以有必要建立许多石油化工厂。
